Writing and erasing various types of non-volatile memory can cause damage to the storage medium. For example, in flash memory, which stores data by storing charge on a floating gate, writing and erasing may damage the tunnel oxide layer between the substrate and the floating gate, creating sites in the oxide layer that trap charge carriers. Charge storage and leakage via trap sites may cause data errors. Thus, as the density of trap sites increases due to repeated writing and erasing, data error rates may also increase. Cumulative damage caused by repeated writing and erasing may limit the useful lifetime of various types of non-volatile memory.
Annealing certain types of non-volatile memory at higher-than-operating temperatures may reverse damage caused by repeated writing and erasing. For example, thermal annealing of flash memory may provide sufficient energy to restore trap sites to their original state, thereby reducing the number of defects and improving the longevity and endurance of an annealed memory device. However, annealing temperatures may themselves cause charge leakage and data errors, making it impractical to anneal operating non-volatile memory.